Pure silicon and germanimum are

Options

A. conductors
B. semiconductors
C. insulators
D. piezoelectric crystals

Explanation

To solve the question "Pure silicon and germanium are conductors, semiconductors, insulators or piezoelectric crystals," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Elements**:
- We need to analyze pure silicon (Si) and germanium (Ge). Both of these elements belong to Group 14 of the periodic table.

2. **Determine Valence Electrons**:
- Silicon and germanium each have 4 valence electrons. This is significant because the number of valence electrons determines the electrical properties of the material.

3. **Understand Electrical Conductivity**:
- Materials can be classified based on their ability to conduct electricity:
- **Conductors**: Materials that allow electricity to flow easily (e.g., metals).
- **Insulators**: Materials that do not allow electricity to flow easily (e.g., rubber, glass).
- **Semiconductors**: Materials that have conductivity between conductors and insulators. They can conduct electricity under certain conditions, such as the presence of impurities or when heated.
- **Piezoelectric Crystals**: Materials that generate an electric charge when mechanical stress is applied.

4. **Analyze Silicon and Germanium**:
- Although silicon and germanium have 4 valence electrons, they do not have free electrons at absolute zero temperature, which means they do not conduct electricity well at low temperatures. However, they can conduct electricity under certain conditions, such as when they are doped with impurities (making them semiconductors).

5. **Conclusion**:
- Based on the analysis, pure silicon and germanium are best classified as **semiconductors** because they can conduct electricity under certain conditions, unlike insulators which do not conduct electricity at all.

### Final Answer:
Pure silicon and germanium are **semiconductors**.

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